1. Technical Field
The following relates to connectors used in coaxial cable communications, and more specifically to embodiments of a connector that improve the clamping of a center conductor.
2. State of the Art
Coaxial cables are electrical cables that are used as transmission lines for electrical signals. Coaxial cables are composed of a center conductor surrounded by a flexible insulating layer, which in turn is surrounded by an outer conductor that acts as a conducting shield. An outer protective sheath or jacket surrounds the outer conductor. Each type of coaxial cable has a characteristic impedance which is the opposition to signal flow in the coaxial cable. The impedance of a coaxial cable depends on its dimensions and the materials used in its manufacture. For example, a coaxial cable can be tuned to a specific impedance by controlling the diameters of the inner and outer conductors and the dielectric constant of the insulating layer. All of the components of a coaxial system should have the same impedance in order to reduce internal reflections at connections between components. Such reflections increase signal loss and can result in the reflected signal reaching a receiver with a slight delay from the original. Return loss is defined loosely as the ratio of incident signal to reflected signal in a coaxial cable and refers to that portion of a signal that cannot be absorbed by the end of coaxial cable termination, or cannot cross an impedance change at some point in the coaxial cable line.
Two sections of a coaxial cable in which it can be difficult to maintain a consistent impedance are the terminal sections on either end of the cable to which connectors are attached. A coaxial cable in an operational state typically has a connector affixed on one or either end of the cable. These connectors are typically connected to complementary interface ports or corresponding connectors to electrically integrate the coaxial cable to various electronic devices. The center conductor of the coaxial cable carries an electrical signal and can be connected to an interface port or corresponding connector via a conductive union between the connector and the center conductor. The contact of the conductive union is critical for desirable passive intermodulation (PIM) results. However, the axial displacement associated with a connector moving into a closed position from an open position often times adversely affects the contact between the center conductor and the connector and/or the distance between conductors. The result of a poor conductive union between the center conductor and the connector leads to diminished performance of the connector in transmitting the electrical signal from the cable to the integrated electronic device. Likewise, the result of altering the distance between conductors introduces deviation from the characteristic impedance of the cable and results in diminished performance of the connector.
In field-installable connectors, such as compression connectors or screw-together connectors, it can be difficult to maintain acceptable levels of passive intermodulation (PIM). PIM in the terminal sections of a coaxial cable can result from nonlinear and insecure contact between surfaces of various components of the connector. Moreover, PIM can result from stretching or cracking various component parts of the connector during assembly. A nonlinear contact between two or more of these surfaces can cause micro arcing or corona discharge between the surfaces, which can result in the creation of interfering RF signals. For example, some screw-together connectors are designed such that the contact force between the connector and the outer conductor is dependent on a continuing axial holding force of threaded components of the connector. Over time, the threaded components of the connector can inadvertently separate, thus resulting in nonlinear and insecure contact between the connector and the outer conductor.
Where the coaxial cable is employed on a cellular communications tower, for example, unacceptably high levels of PIM in terminal sections of the coaxial cable and resulting interfering RF signals can disrupt communication between sensitive receiver and transmitter equipment on the tower and lower-powered cellular devices. Disrupted communication can result in dropped calls or severely limited data rates, for example, which can result in dissatisfied customers and customer churn.
Current attempts to solve these difficulties with field-installable connectors generally consist of employing a pre-fabricated jumper cable having a standard length and having factory-installed soldered or welded connectors on either end. These soldered or welded connectors generally exhibit stable impedance matching and PIM performance over a wider range of dynamic conditions than current field-installable connectors. These pre-fabricated jumper cables are inconvenient, however, in many applications.
For example, each particular cellular communication tower in a cellular network generally requires various custom lengths of coaxial cable, necessitating the selection of various standard-length jumper cables that is each generally longer than needed, resulting in wasted cable. Also, employing a longer length of cable than is needed results in increased insertion loss in the cable. Further, excessive cable length takes up more space on the tower. Moreover, it can be inconvenient for an installation technician to have several lengths of jumper cable on hand instead of a single roll of cable that can be cut to the needed length. Also, factory testing of factory-installed soldered or welded connectors for compliance with impedance matching and PIM standards often reveals a relatively high percentage of non-compliant connectors. This percentage of non-compliant, and therefore unusable, connectors can be as high as about ten percent of the connectors in some manufacturing situations. For all these reasons, employing factory-installed soldered or welded connectors on standard-length jumper cables to solve the above-noted difficulties with field-installable connectors is not an ideal solution.
Accordingly, during movement of the connector and its internal components when mating with a port, the conductive components may break contact with other conductive components of the connector or conductors of a coaxial cable, causing undesirable passive intermodulation (PIM) results. For instance, the contact between a center conductor of a coaxial cable and a receptive clamp is critical for desirable passive intermodulation (PIM) results. Likewise, poor clamping of the coaxial cable within the connector allows the cable to displace and shift in a manner that breaks contact with the conductive components of the connector, causing undesirable PIM results. Furthermore, poor clamping causes a great deal of strain to the connector.
Thus, there is a need for an apparatus that addresses the issues described above, and in particular there is a need for a coaxial cable assembly and method that provides an acceptable conductive union between the conductors of the coaxial cable and the connector.